The cyclicity property is lost when considering the sum of the \(s\) - and \(u\) -channel as in Eq. (REF ). By inspecting the resulting polytope
Ref. [1]} observed that it is “almost cyclic” in the sense that the only boundaries which are not of the type \((i , i+1 , j , j+1)\)  in the example considered above involve low-spin partial waves in Eq. (REF ) and can be found by direct inspection. This is what we also find and this is the strategy of finding bounds that we follow in this paper. In particular, we do not prove that the set of bounds found in this way is complete (even though we suspect it to be the case). It would be very interesting to rigorously demonstrate this.
